OT: I really need to ask - Electrical question

[theripley]

I just called the end user, they confirmed that the fault appeared after installation of 4 manual call points on the 5th zone. They also said that there were no sensors added to the said zone, only manual call points.

 

[Gil47]

P1 and P2 both have an on off switch in each lead, along with a fuse in each lead, so the power supply is designed to cope with either P1 or P2 being the phase supply, or for that matter the neutral, or could be from an isolating transformer supply.

Now in the Philippines you are used to the Neutral being connected to the Earth at the main switchboard, now this is not always the case in other countries.

To confirm which is Phase and which neutral, test the voltage to earth from P1 and then from P2, one will be less than a volt or two this will be the neutral the one with a higher voltage 110 or 230 volts, I think the Philippines supply voltage is 230, now that one will be the phase..


My reference to End of line resistors was made thinking you were dealing with manual call points

 

[Lancie1]

Please correct me with this, but with what I have known, to ensure correct wiring, neutral must be connected to ground.

Erika, whether a neutral even exists depends on the type of wiring, on the upstream transformer configuration (Delta-Wye, Delta-Delta, Wye-Delta). Whether the neutral is connected to Earth potential again depends on the situation. For example, for many industrial plant electrical systems, a main 7200 to 480-volt 3-phase delta-delta (star to star winding) main utility transformer feeds the plant electrical distribution panel. For this system, there is no hard ground point because the star secondary winding does not have a 0 voltage point (all terminals measure 480 volts to earth ground). For this type of system, often a special grounding arrangement is needed.

For 240/120 volt residential wiring in the US, there is a neutral and it is required to be grounded. For your 220 volt wiring in the Philippines, I do not know, but probably one leg is normally grounded. From your drawing it is impossible to know whether that is always the P2 leg. As Gil pointed out, even if it is always supposed to be P2, do not assume that it was wired correctly, but check it with a meter.

Electricians and others do make mistakes. For the house that I moved into recently, I found many of the receptacles with no connected ground, and some receptacles with the hot and neutral wires swapped. It is smart to check and not assume that any wiring is as it should be.

 

[theripley]

Thanks a lot for helping y'all. You're all great.

When I started this thread, I was assuming they added sensors but now it is confirmed there were none, only manual call points. I will be checking this system by the weekend with 1 of my technicians. I hope we get this right.

I will keep you updated.

 

[theripley]

Update.

Because of this thread I was or we, I mean "we" all troubleshooted the fire alarm system. It is now working well. The problem was ground potential with one of the buzzer lead, we condemned it. Another problem is that on this zone, the sensors are not connected in one loop. Our recommendation is re-wiring to make it single-loop.

Thank you all so much.

 

[Lancie1]

Thanks for the feedback. It sounds like you did a good job on finding the problem.

 

[theripley]

Thanks for the feedback. It sounds like you did a good job on finding the problem.

Thanks for being helpful.